Gardeners have been fussing with fertilizers since the first human stuck a seed in soil. The goal of fertilization is to create the richest soil possible, since it is in the soil where plants draw the essential nutrients that make them grow.

Organic gardeners rely on fertilizers made from plants and animal by-products, avoiding the chemical fertilizers that have flooded the farming and gardening industries for the past 50 years. Synthetic fertilizers do nothing to support the microbial activity that makes soil and plants healthy. In fact, some of them will kill your soil.

These fertilizers also short-change your plants by supplying them only with the major elements nitrogen, phosphorus and potassium, while overlooking the other 13 nutrients plants need to survive. And, if that's not enough, it's been proven that chemical fertilizers leach into our water supply much more easily than organic fertilizers, thereby polluting it.

It's no wonder many organic gardeners reject these synthetics and rely on old standbys like bone meal, blood meal and fish emulsion. But times are a-changin', and even these additives, variations of which have been used for centuries, are coming under scrutiny.

We Calls 'Em Like We Sees 'Em

Blood meal, bone meal and fish emulsion are just what they say they are: the remains of blood, bones and fish. The first two products come from cattle slaughterhouses, where bones and blood are dried, crushed and packaged for gardeners. Fish emulsion and other fish-based products are made from carcasses left over at fish-processing plants, though sometimes fish are caught specifically to be used as fertilizer.

Right about now, the vegetarian gardeners in the crowd are raising their eyebrows and squirming in their seats. Even borderline carnivores might find this information a bit jarring. Couple this with the threat of mad cow disease, which can be transmitted through bone meal and blood meal, and it's enough to get some gardeners looking for vegetarian alternatives.

Moo-Free Zone

I checked in with the folks at Palo Alto's Common Ground organic-gardening store, where founder John Jeavons has produced a pamphlet, "Recommended Organic Soil Amendments," that lists readily available organic-fertilizer alternatives and recommended quantities.

The store is the not-for-profit project of Jeavons' Ecology Action, an organization devoted to developing techniques for growing more nutritious food while simultaneously increasing the health of the soil.

According to the store's Eva Henin, Common Ground began emphasizing a vegetarian approach to fertilizers as a result of the threat of mad cow disease and not because of any vegetarian inklings. Henin quotes John Robbins, author of " The Food Revolution," who says the US meat industry talks about mad cow disease in terms of "when," not "if," the disease will hit our shores, and though the US Department of Agriculture placed import restrictions on European bone meal and blood meal in December 2000, Jeavons decided to head off any possible complications by encouraging the use of non-animal-based fertilizers.

Begin at the Beginning

Before adding anything to your soil, be it vegetarian or not, consider performing a soil test. How do you know what to add if you don't know what your soil already contains? Soil tests come in varying levels of complexity, from simple, store-bought do-it-yourself kits that will determine your soil's pH level to lab tests that will give you a full nutrient breakdown.

The San Francisco League of Urban Gardeners offers an inexpensive lab test that will reveal the most intimate details regarding your soil. The results come with complete recommendations for additives, including amounts to use. (I wish I'd followed this advice when I started my garden. When I finally got around to the test, the results provided a wealth of information that would have saved me time and money.)

For more information about soil tests, see the August 23 Green Gardener column.

The Substitutes

Whether your soil test says your garden needs potash, phosphorus or nitrogen, non-animal-based by-products are readily available at most nurseries. The following information, unless credited otherwise, is from Jeavons' pamphlet. The amounts stated are for use on a 100-square-foot garden of poor-quality clay soil in the garden's first year.

Whichever of these fertilizers you choose to use, work them into the soil a good 6 to 8 inches before you plant anything. Cut quantities back appropriately if you have a smaller garden, and feel free to experiment. As Jeavons reminds readers in his pamphlet, "Soil conditions can vary from backyard to backyard."

Compost

First and foremost in Jeavons' plan is the use of compost to improve and maintain the soil's health. A rich, black soil-like amendment made from rotted yard waste and kitchen scraps, compost feeds soil microbes that release nutrients. Nothing else provides the necessary carbohydrates and cellulose, as well as all 16 nutrients plants need.

In fact, if your soil is in good shape, he suggests you add a 1-inch layer of compost (8 cubic feet, or a dozen 5-gallon buckets), a quarter-pound of potash and a half-pound of calcium to your garden.

Supporting this advice, the July/August 2000 issue of Organic Gardening magazine included a special report on fertilizers, based on research performed at the Woods End Research Laboratory, in Mt. Vernon, Maine. The research concluded that if gardeners use a combination of compost, mulch and cover crops, they need add nothing else to their soil: If your soil is healthy and alive, it will provide plants with all the nutrients they need.

On the other hand, "Golden Gate Gardening," by Pam Peirce, recommends that you routinely add a 2-inch layer of compost with some nitrogen and phosphorus to your vegetable garden. (Ask three gardeners the same question, and I guarantee you'll get three different answers, which is why in the world of gardening, we all need to become our own authority. There are too many variables for anyone to have the definitive answer for many questions regarding your particular garden's needs.) Nitrogen

If you want to add nitrogen to your soil, try using alfalfa meal or the alfalfa pellets sold for rabbit feed, instead of blood meal or fish emulsion. Alfalfa is a quick-acting source of nitrogen, with healthy amounts of phosphorus and potash. Organic Gardening magazine called rabbit pellets "an excellent all-purpose fertilizer." Jeavons recommends adding 16 pounds of alfalfa meal to your garden.

Phosphorus

Rather than using bone meal as your source of phosphorus, try soft-rock phosphate. Dig 6 pounds into your plot.

Potash

For potash, try 1 pound of kelp meal or 8 1/2 pounds of crushed granite, which Jeavons says will last for 10 years, slowly releasing potash and trace minerals.

Lisa Van Cleef is a feral office worker who escaped into the garden never to return. The Green Gardener name is, of course, a tribute to the great Joe Carcione, The Greengrocer, whose reporting was useful, no-nonsense and funny as hell.